[R] eliminating a large subset of data from a frame

Uwe Ligges ligges at statistik.uni-dortmund.de
Fri Sep 5 18:16:20 CEST 2003

Peter Whiting wrote:

> I have a data frame with 155,000 rows. One of the columns
> represents the user id (of which about 10,000 are unique).  I am
> able to isolate 1000 of these user ids (stored in a list) that
> I want to eliminate from the data set, but I don't know of an
> efficient way to do this. Certainly this would be slow:
> newdf<-df
> for(i in listofbadusers) {
>  newdf<-subset(tmp,uid!=i)
> }

What about subsetting? See help("[").

One solution (not saying it is the optimal one):

  newdf <- df[!(df$uid %in% listofbadusers), ]

Uwe Ligges

> is there a better approach?
> I guess I could use the opposite logic and use a list of
> good users and add their data to the new frame...
> thanks,
> pete
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